Invasive ophthalmic surgeries often lead to numerous complications for patients, at least in part because patient compliance with prophylactic drugs after ophthalmic surgery is relatively low and in part because the ocular bioavailability is frequently low for common dosage forms. The vast majority of ophthalmic drug formulations remain the traditional solutions, ointments and suspensions, by one estimate accounting for about 90% of the global market of ophthalmic drug formulations.
Even when patient compliance is high, the ocular bioavailability of drugs applied topically as eye-drops is very poor. The absorption of drugs in the eye is severely limited by some protective mechanisms that ensure the proper functioning of the eye. The contact with the absorbing surfaces (cornea and sclera) is reduced to a maximum of about two minutes. Dosage volumes are limited by drainage via the nasolacrimal system into the nasopharynx and the gastrointestinal tract. Lacrimation and the physiological tear turnover (16% per minute in humans in normal conditions) are often increased by the instillation even of mildly irritating solutions, leading to more rapid clearance of the applied dosage form.
Trabeculectomy is an ophthalmic surgical procedure used in the treatment of glaucoma. Removing part of the eye's trabecular meshwork and adjacent structures allows drainage of aqueous humor from within the eye to underneath the conjunctiva to relieve intraocular pressure. The scleral flap is typically sutured loosely back in place with several sutures. Common complications include blebitis (an isolated bleb infection typically caused by microorganisms such as Staphylococcus epidermidis, Propriobacterium acnes, or Staphylococcus aureus), inflammation, and bleb-associated endophthalmitis.
Endophthalmitis is an inflammation of the ocular cavities and their adjacent structures. It is a possible complication of all intraocular surgeries, particularly cataract surgery, which can result in loss of vision or the eye itself. Endophthalmitis is usually accompanied by severe pain, loss of vision, and redness of the conjunctiva and the underlying episclera. Infectious etiology is the most common and various bacteria and fungi have been isolated as the cause of the endophthalmitis. The patient needs urgent examination by an ophthalmologist and/or vitreo-retina specialist who will usually decide for urgent intervention to provide intravitreal injection of potent antibiotics and also prepare for an urgent pars plana vitrectomy as needed. Enucleation may be required to remove a blind and painful eye.
Ophthalmic sutures are commonly used during ophthalmic surgical procedures, including trabeculectomy as well as pterygium removal, cataract surgery, strabismus correction surgery, penetrating keratoplasty, sclerectomy, and conjunctival closure. The choice of suture material can strongly impact the occurrence of complications related to infection and inflammation post ophthalmic surgery, either causing irritation and local inflammation or providing a substrate for microorganism growth. The suture materials typically employed include nonbiodegradable ophthalmic suture materials such as ETHILON® nylon suture, MERSILENE® polyester fiber suture, PERMA-HAND® silk suture, PROLENE® polypropylene suture, each commercially available from Ethicon, Somerville, N.J.; and VASCUFIL® coated monofilament suture composed of a copolymer of butylene terephthalate and polyteramethylene ether glycol, MONOSOF˜DERMALON® monofilament nylon sutures composed of long-chain aliphatic polymers Nylon 6 and Nylon 6.6, NOVAFIL® monofilament sutures composed of a copolymer of butylene terephthalate and polyteramethylene ether glycol, SOFSILK® braided sutures composed of fibroin, TI-CRON-SURGIDAC® braided polyester sutures composed of polyester terephthalate, SURGILON® braided nylon sutures composed of the long-chain aliphatic polymers Nylon 6 and Nylon 6.6 and SURGIPRO II-SURGIPRO® sutures composed of polypropylene, each commercially available from U.S. Surgical, Norwalk, Conn.
Ideally, ophthalmic suture materials would be biodegradable and biodegradable over the useful suture lifetime, retaining the requisite tensile strength and capable of delivering therapeutic or prophylactic agents to increase patient success. For pterygium removal, cataract surgery and strabismus correction surgery, sutures could be used to close the wound and release antibiotic and anti-inflammatory drugs. For trabeculectomy surgeries, sutures could be placed on sclera flaps providing local chemotherapeutic agents, decreasing production of scar tissue, and also, on conjunctival closure with antibiotic release. In penetrating keratoplasty, the sutures hold the graft, as well as release antibiotic and immunosuppressant agents.
Therefore, it is an object of the invention to provide ophthalmic sutures that are biocompatible and biodegradable and retain the requisite tensile strength over the useful life of the suture.
It is further an object of the invention to provide ophthalmic sutures capable of delivering an effective amount of one or more therapeutic or prophylactic agents to the ocular region over an extended period of time.
It is further an object of the invention to provide ophthalmic sutures having a diameter allowing for use in ophthalmic procedures while causing little to no irritation of the surrounding tissue.
It is further an object of the invention to provide the ophthalmic sutures having a higher tensile strength than commonly employed ophthalmic suture materials of a similar diameter.
It is further an object of the invention to provide methods of making ophthalmic sutures that are biocompatible and biodegradable and capable of delivering one or more therapeutic agents.
It is further an object of the invention to provide method of ophthalmic surgery and repair using the sutures described herein to increase patient comfort and/or success as compared to traditional ophthalmic suture materials.